1. Field of the Invention
With reference to the classification of art as established in the United States Patent & Trademark Office the present invention is found in the general Class entitled, "Sheet Feeding or Delivering" (Class 271) and in the subclass therein entitled, "for front and side alignment of sheet" (subclass 236). Additionally note is made of the general Class entitled, "Drying and Gas or Vapor Contact with Solids" (Class 34) and the subclass therein entitled, "with treated material motion" (subclass 33).
2. Description of the Prior Art
The prior art has few patents directed to the stacking, restacking and aeration and vibration of stacks of printed sheets of paper, cardboard and the like. Among those known are the patents to RUUD as in U.S. Pat. Nos. 3,418,725 and 3,656,743. In these and other known apparatus for aligning the edges of stacked sheets it is believed to be new and novel to provide vibrating shoes which support the load and to direct a controlled blast of air through apertures in these shoes. This aeration has produced very satisfactory separation of sheets which are attracted to each other by only partially dried printing ink, static electricity or other naturally occurring conditions. Whether the shoes are flat or have an upward contour to simultaneously displace the edge arranged stack of material, the combination of vibration and blast of air at this vibration point provides a desired positive separation of the sheets in the stack.
Whereas the prior art devices, as shown in RUUD, employ air directed downwardly at the top of the sheets this seems to cause many of the sheets to cling together rather than separate as desired. In the preferred arrangement of the present invention there is provided automatic control means for directing an air blast to either the leading portion or trailing portion of the stack on the vibrating shoes. Whereas the RUUD vibrating device is by electromagnetic means it has been found advantageous to use a pneumatic vibrator so both the amplitude and frequency of the vibrations can be changed to suit the sheets being restacked.
In the present invention the air blast, as directed upwardly at and from the vibrating shoes, is of a larger volume and less velocity at the middle of the shoes than at the outer edges where a greater initial blast seems to be required to insure complete and positive separation of the sheets. An adjustable backstop is provided in the present apparatus so that the stack of paper, cardboard or the like is positioned in relation to the skid to restack the sheets in the desired position on the skid platform. Cutoff provision is provided on the air supply to the shoes so that where a shoe is not in contact with a stack of sheets the air to that shoe is cut off so as to maintain the desired air flow and pressure to the remaining shoes in vibrating engagement with the stack.